In recent years, thin batteries have been used as power sources for small-sized electronic equipment such as biological wearable devices, portable telephones, recording and playing-back devices, wristwatches, video and still cameras, liquid crystal displays, electronic calculators, IC cards, temperature sensors, hearing aids, and pressure-sensitive buzzers. Such thin batteries are required to have flexibility. For example, a thin battery to be mounted to a biological wearable device or a wearable portable terminal is required to be deformed in response to the movement of a living body. Thus, a thin battery having a housing made of a thin and flexible laminate film has been proposed (see PTL 1).